1. Field of the Invention
The present invention relates to a method for measuring the cuticle scale height of fibers and, more particularly, to an objective and reliable method for the measurement of the cuticle scale height of naturally occurring, proteinaceous fibers employing a scanning electron microscope (SEM).
2. Description of the Prior Art
About 16,000 tons of raw cashmere are produced globally each year. Approximately 50% of raw cashmere is lost to scouring and dehairing, meaning that global production of cashmere for use in garments is about 8000 tons or 16,000,000 pounds. The United States definition of cashmere for testing by The American Association of Textile Chemists and Colorists (AATCC) was broadened in 2001 by increasing the average diameter for cashmere from 15-16 microns to 15-18.5 microns average, meaning that a wider range of specialty animal fibers, such as yak, could more readily be substituted for cashmere with a lessened expectation of detection.
Recent prices for dehaired dark Afghan cashmere are $41 per kilo whereas dehaired medium yak hair is $15 per kilo. Even greater differences in price exist between white Chinese cashmere at $69 per kilo and 17 micron wool at $8.83/kilo. Numerous articles in the literature, court cases, and the continuing search for new analytical technologies have all pointed to the need for increased accuracy and objectivity in the quantitative analysis of intimate blends of cashmere with wool.
Several different types of technology have been brought to bear on the problem of accurate repeatable objective blend analysis of cashmere blends, a sign in itself that the problem is an important one that merits research effort to determine a better test method. This need is consistent with society's broader demand over time for standardized measurement techniques in commerce [1]. DNA probes, electrophoresis of extracted amino acids, high pressure liquid chromatography of treated fibers, Fourier transform infra-red analysis both with and without neural nets as well as image analysis both with and without neural nets have all been applied to the problem of increasing the accuracy of cashmere intimate blend analysis [2, 3, 4, 5, 6, 7, 8, 9]. Notwithstanding these efforts, published research indicates that both scanning electron microscope based testing and, indeed, all other applied technologies to date, including both transmitted light microscopy and scanning electron microscopy, are deficient in their ability to consistently and objectively differentiate between cashmere and other animal fibers [7].
Cuticle scale height measurement for the objective determination of blend type has been claimed to be able to categorically and without exception differentiate objectively between wool and all specialty animal fibers [8]. International Wool Textile Organization Test. Method (IWTO) 58 embodies the work performed by various researchers on quantitative blend analysis using SEM, particularly The German Wool Research Association. While IWTO 58—displays large amounts of data on cuticle scale height, it gives no specific instructions on exactly where, how, or how many scales should be measured in order to derive scale height [9].
The scale heights of fibers in IWTO 58 and all other documents concerning scale height to date are obtained by measuring the scales while the fibers snippets are lying down longitudinally. Early animal textile fiber researchers [10] realized the limitations of this method in that profile artifacts and limited scale views are often presented for measurement and uninterrupted sequential scale height measurement is prevented.
Using the traditional method, scale height measurements are taken by focusing on a scale edge at 10000× or higher while the fiber snippet is lying longitudinally on an SEM stub. After this scale is measured another measurable scale edge may be sought after, although no sample size number of scales to be measured is given. The SEM operator then hunts along the fiber surface until he or she subjectively judges that an appropriate scale has presented itself for measurement. This process interjects an unavoidable element of the personal equation into the process of cuticle scale height measurement which may, in part, be responsible for the difficulty experienced in the consistent use of this technique.